Apparatus, system, and method for low cost high resolution chemical detection

Abstract

An apparatus, system, and method are disclosed for low cost high resolution chemical detection. The apparatus includes two outer sealing bodies with flow channels etched into the bodies. Two gas chromatography (GC) columns are between the outer bodies, with a valve that switches flow regimes from series flow through the two GC columns to sample flowing directly to each GC column. The flow regimes are achieved with a single pump or dual pumps, and with one to three flow restrictions. The apparatus includes a preconcentration tube for concentrating chemicals of interest from the sample, and a sample switching valve and sampling pump to switch the sample flow from concentrating sample to delivering concentrated sample. The apparatus includes an engineered leak to equalize flow between a sample channel and a detector circuit. The sample channels may have impermeable inserts allowing the apparatus to measure chemicals in the parts-per-billion range.

1. An apparatus for high resolution chemical detection, comprising:
 a first outer sealing body and a second outer sealing body; a plurality of flow channels etched into the first outer sealing body and the second outer sealing body; a first gas chromatography (GC) column and a second GC column interposed between the first and second outer sealing bodies; 
 and a valve that switches between a first flow regime and a second flow regime, wherein the first flow regime comprises a sample flowing through the first GC column then the second GC column, and wherein the second flow regime comprises the sample flowing to the second GC column without flowing through the first GC column. 
 
   
   
     2. The apparatus of  claim 1 , wherein the valve is a solenoid valve. 
   
   
     3. The apparatus of  claim 1 , further comprising a first pump, a first resistance, a second resistance, and a third resistance, wherein: the first flow regime further comprises a first fluid stream from the first pump that flows through the first GC column and the second GC column, and a second fluid stream directed by the valve that flows through the second resistance and the first resistance; and the second flow regime further comprises a third fluid stream from the first pump that flows through the first GC column and the first resistance, and a fourth fluid stream directed by the valve that flows through the third resistance and the second GC column, wherein the fourth fluid stream further prevents the third fluid stream from flowing through the second GC column. 
   
   
     4. The apparatus of  claim 1 , further comprising a first pump and a second pump, and a first resistance, wherein: the first flow regime further comprises a first fluid stream from the first pump that flows through the first GC column and the second GC column, and a second fluid stream directed by the valve from the second pump that flows through the first resistance, wherein the second stream further prevents the first stream from flowing through the first resistance; and
 the second flow regime further comprises a third fluid stream from the first pump that flows through the first GC column and the first resistance, and a fourth fluid stream directed by the valve from the second pump that flows through the second GC column, wherein the fourth stream further prevents the third stream from flowing through the second GC column. 
 
   
   
     5. The apparatus of  claim 1 , further comprising a first pump, a first resistance, and a fourth resistance, wherein: the first flow regime further comprises a first fluid stream from the first pump that flows through the first GC column and the second GC column, and a second fluid stream directed by the valve that flows through the fourth resistance and the first resistance; and
 the second flow regime further comprises a third fluid stream from the first pump that flows through the first GC column and the first resistance, and a fourth fluid stream directed by the valve that flows through the fourth resistance and the second GC column, wherein the fourth fluid stream further prevents the third fluid stream from flowing through the second GC column. 
 
   
   
     6. The apparatus of  claim 5 , wherein each resistance comprises a flow resistor selected from the flow resistors consisting of an orifice, a controllable valve, and a microboard with porous substrate. 
   
   
     7. The apparatus of  claim 1 , wherein at least one of the plurality of flow channels further comprises an impermeable insert interposed between the first and second outer sealing bodies. 
   
   
     8. The apparatus of  claim 7 , wherein the impermeable insert comprises one of a quartz insert and a ceramic insert. 
   
   
     9. The apparatus of  claim 8 , further comprising a detector circuit that detects a target chemical eluting from the first and second GC columns, wherein the target chemical occurs in an ambient environment at less than about 1,000 parts-per-billion. 
   
   
     10. The apparatus of  claim 1 , further comprising a preconcentration tube, a sampling pump, and a sample switching valve, wherein: the preconcentration tube comprises a preconcentration material that adsorbs and desorbs chemicals from an intake air stream; and the sample switching valve switches between a concentration mode and sensing mode, wherein the concentration mode comprises the intake air stream flowing through the preconcentration tube in a first direction, and a the sampling pump sending a dilute sample through a GC unit comprising the first and second GC columns, and wherein the sensing mode comprises the intake air stream flowing through the preconcentration tube in a second direction, and the sampling pump sending a concentrated sample through the GC unit. 
   
   
     11. The apparatus of  claim 10 , wherein the preconcentration material releases a known chemical at a specified temperature, the apparatus further comprising an internal standard delivery module configured to heat the preconcentration material to the specified temperature, and a calibration module configured to detect elution of the known chemical from the GC unit. 
   
   
     12. The apparatus of  claim 11 , wherein the preconcentration material comprises an adsorbent resin. 
   
   
     13. The apparatus of  claim 1 , further comprising a detector circuit interposed between the first and second outer sealing bodies, wherein the detector circuit comprises a detector circuit seal, and wherein the apparatus further comprises a pressure equalizing channel configured to equalize a first pressure in a sample channel with a second pressure in the detector circuit. 
   
   
     14. The apparatus of  claim 13 , further comprising at least one spring interposed between the first and second outer sealing bodies, wherein the at least one spring applies force to enhance the detector circuit seal. 
   
   
     15. A method for high resolution chemical detection, comprising:
 providing a first outer sealing body and a second outer sealing body; etching a plurality of flow channels into the first outer sealing body and the second sealing body; providing a first gas chromatography (GC) column and a second GC column interposed between the first and second outer sealing bodies; providing a valve that switches between a first flow regime and a second flow regime; operating the valve in the first flow regime by flowing a sample through the first GC column and then the second GC column; and operating the valve in the second flow regime by flowing the sample through the second GC column without flowing the sample through the first GC column. 
 
   
   
     16. The method of  claim 15 , further comprising flowing an intake air stream through a preconcentration tube in a first direction to concentrate chemicals on the preconcentration tube, and flowing the intake air stream through the preconcentration tube in a second direction to deliver a concentrated sample through a GC unit comprising the first and second GC columns. 
   
   
     17. The method of  claim 16 , further comprising heating the preconcentration tube to a specified temperature thereby releasing a known chemical from the preconcentration tube, and detecting elution of the known chemical from the GC unit. 
   
   
     18. The method of  claim 15 , further comprising providing a detector circuit interposed between the first and second outer sealing bodies, and providing a detector circuit seal. 
   
   
     19. The method of  claim 18 , further comprising providing a pressure equalizing channel from a sample channel to the detector circuit. 
   
   
     20. A gas-chromatography sensor comprising: a first outer sealing body and a second outer sealing body; a plurality of flow channels etched into the first outer sealing body and the second outer sealing body; a first gas chromatography (GC) column and a second GC column interposed between the first and second outer sealing bodies; a valve that switches between a first flow regime and a second flow regime, wherein the first flow regime comprises a sample flowing through the first GC column then the second GC column, and wherein the second flow regime comprises the sample flowing to the second GC column without flowing through the first GC column; and a preconcentration tube, a sampling pump, and a sample switching valve, wherein: the preconcentration tube comprises a preconcentration material that adsorbs and desorbs chemicals from an intake air stream; and the sample switching valve switches between a concentration mode and sensing mode, wherein the concentration mode comprises the intake air stream flowing through the reconcentration tube in a first direction, and the sampling pump sending a dilute sample through a GC unit comprising the first and second GC columns, and wherein the sensing mode comprises the intake air stream flowing through the preconcentration tube in a second direction, and the sampling pump sending a concentrated sample through the GC unit.